Concrete, pavers, beds have straight or curved edges. Belgian Block as an irregular shape that moves in and out a bit. This is especially the case if the block is setup vertically. Older installations may also have a block that shifted, again especially if vertical. In some towns, it is used on the streets even if the driveways have no blocks.

Trimmer? Edger? Something else? Is there a special technique that works best? It would seem the edger runs a risk of hitting a block and possibly damaging it or damaging itself.